1. Field of the Invention
The present invention relates to a vehicle control unit, having a function of preventing a breakdown of a vehicle caused by an operator's erroneous operation in a vehicle stop state, and a vehicle equipped with the vehicle control unit, and more particularly, to a vehicle control unit suitable for an industrial vehicle and a vehicle equipped with the vehicle control unit.
2. Description of the Related Art
Generally, in a vehicle, a driving force of an engine is transmitted to a transmission via a torque converter, and is transmitted to a drive wheel via one of a forward clutch and a reverse clutch received in the transmission, thereby allowing the vehicle to be in a traveling mode. The forward clutch and the reverse clutch are selected by a shift lever used to perform a forward/reverse switching operation.
A control system of a general automatic transmission includes a forward solenoid and a reverse solenoid of an electromagnetic switching valve for controlling a drive mechanism involved with a forward/reverse operation of a shift vehicle; and a control device for controlling the forward and reverse solenoids, wherein an operator selects a shift position by operating a shift lever provided in a driver seat, and the solenoids are controlled to be turned on or off on the basis of the shift position of the shift lever detected by a control unit, thereby realizing the speed stages such as a neutral, a forward/reverse, and plural speed stages.
In such a vehicle, it is desirable that the operator operates an accelerator pedal after performing a shift operation from the neutral to the forward or the reverse upon carrying out a departure operation. However, when the operator erroneously operates the accelerator pedal before the shift operation, a problem may arise in that an engine rpm increases (for example, the accelerator pedal pressing operation and the shift change operation are simultaneously carried out in a vehicle stop state). In this case, when a transmission gear is engaged in accordance with the erroneous shift operation, a problem may arise in that a transmission, an axle, or the like is broken down due to a large shock.
Patent Document 1 (Japanese Patent No. 2877252) discloses a device for preventing a sudden departure caused by an operator's erroneous operation. This device allows a control unit to output a transmission signal to a hydraulic control valve for performing a clutch switching operation on the basis a position selector signal for indicating an operator's position selection, a cutoff signal for indicating a cutoff state, an engine rpm, and a vehicle speed. Accordingly, when the vehicle travels at a vehicle speed not more than a predetermined vehicle speed in a state where the transmission is located at a neutral and the engine is at a high rpm, it is possible to prevent a case in which the vehicle shoots off due to a clutch engagement in accordance with the operator's erroneous operation.
As described above, in the vehicle stop state, when the operator carries out the erroneous operation in which the engine rpm increases at the same timing as the shift operation or at a timing just before or after the shift operation upon carrying out the departure operation, a problem may arise in that the transmission, the axle, or the like is broken down due to a large shock. Particularly, in an industrial vehicle represented as a cargo handling machine such as a forklift or a reach stacker and a construction machine such as a motor grader, a bulldozer, or a wheel loader, the forward/reverse switching operation is frequently repeated since the driving operation is carried out in many cases during a work, and thus the operator's erroneous operation may easily occur. For this reason, a vehicle for preventing the problem has been strongly demanded.